Are we closing in on dark matter?

This fall, the Kavli Institute for Cosmological Physics at the University of Chicago and the National Academy of Sciences organized a colloquium that brought together more than 100 cosmologists, particle physicists and observational astrophysicists – three fields now united in the hunt to determine what is dark matter. Their goal: to take stock of the latest theories and findings about dark matter, assess just how close we are to detecting it and spark cross-disciplinary discussions and collaborations aimed at resolving the dark matter puzzle.

So where do things stand?

"Ten years ago, I don't think you would've found astronomers, cosmologists, and particle physicists all agreeing that dark matter was really important," said Michael S. Turner, Rauner Distinguished Service Professor and Director of the Kavli Institute for Cosmological Physics at the University of Chicago. "And now, they do. And all of them believe we can solve the problem soon."

Turner and other organizers of the meeting offered their insights following its conclusion. Also offering his assessment was Edward "Rocky" Kolb, Professor in the Department of Astronomy and Astrophysics at the University of Chicago, where he is a member of the Enrico Fermi Institute and the Kavli Institute for Cosmological Physics. "The excitement now is that we are closing in on an answer, and only once in the history of humans will someone discover it," said Kolb. "There will be some student or postdoc or experimentalist someplace who is going to look in the next 10 years at their data, and of the seven or so billion people in the world that person will discover what galaxies are mostly made of. It's only going to happen once."

Said Maria Spiropulu, Professor of Physics at California Institute of Technology, "I think it's fair to say the discovery is 'around the corner.' If we continue with exclusions, then we have to come up with better ideas." As for what drives them Spiropulu said, "We want to know exactly what [dark matter] is made of. We want to know the dynamics and what it involves. A lot of work is ahead of us. Somebody said that it's not going to be as easy as finding the Higgs. Well, finding the Higgs was extremely nontrivial. Of course, once we find it, it goes in the pool of knowledge and then you say, 'Well, it was easy.'"

Roger Blandford, Director of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University and the SLAC National Accelerator Laboratory, said, "We haven't yet found dark matter, but we are now using exquisite techniques that are tightening the constraints." Regarding the prospects of directly detecting dark matter, "I am most impressed by the relatively rapid progress in sensitivity of yet more approaches to seeking dark matter, or particles associated with dark matter. I think the speed with which these experiments are being brought up is very, very encouraging.

"Now it remains a quite possible outcome that, at the end of the day, we reach a floor and going beneath that is really not practical or feasible. That it just gets too hard to be more sensitive. But we are not there yet, and so there's still quite a lot of discovery space that is open for the experimentalists. They may find nothing; but in my book, that is still discovery."